benameur2020

Superlattices and Microstructures 142 (2020) 106473
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Superlattices and Microstructures
journal homepage: www.elsevier.com/locate/superlattices
Impact of substrate nature and film thickness on physical
properties of antimony trisulphide (Sb2S3) thin films for
multifunctional device applications
S. Ben Ameur a, b, *, B. Duponchel c, G. Leroy b, H. Maghraoui-Meherzi d, M. Amlouk e,
H. Guermazi a, S. Guermazi a
a
Research Unit: Physics of Insulators and Semi Insulator Materials, Faculty of Science of Sfax, Road of Soukra Km 3.5, B.P: 1171 3000, Sfax,
University of Sfax, Tunisia
b
Unit�e de Dynamique et Structure des Mat�eriaux Mol�eculaires (UDSMM) EA 4476, Universit�e du Littoral C^
ote d’Opale, 62228, Calais, France
c
Unit�e de Dynamique et Structure des Mat�eriaux Mol�eculaires (UDSMM) EA 4476, Universit�e du Littoral C^
ote d’Opale, 59140, Dunkerque, France
d
Laboratoire de Chimie Analytique et Electrochimie, Faculty of Science of Tunis, Tunis El Manar University, Tunisia
e
Research Unit: Physics of Semi-conductor devices, Faculty of Science of Tunis, Tunis El Manar University, 2092, Tunis, Tunisia
A R T I C L E I N F O
A B S T R A C T
Keywords:
Antimony trisulphide (Sb2S3)
Film thickness
Flexible polymer substrate
Hydrophobic surfaces
Sb2S3 thin films were deposited with various thickness on glass and flexible polymer Poly­
etherimide (PEI) substrates by simple chemical bath deposition. X-ray diffraction patterns reveal
the formation of polycrystalline films with orthorhombic structure. The Sb2S3 thin films grown on
the PEI substrate are rougher. The enhancement of roughness for Sb2S3/PEI thin films leads to
improve their hydrophobic character. Furthermore, they show high values of contact angle (CA)
around 162� . The absorption coefficient of thin films is determined to be higher than 104 cm 1.
The band-gap energy has been found to be between 1.6 and 2.1 eV as a function of thickness
which related to the variation of structural defects. Thus, the growth of these films significantly
depends on the nature of the substrate and its thickness. The obtained results show that all Sb2S3
on glass and PEI thin films have potential applications in the self-cleaning windows and solar
cells.
1. Introduction
The fabrication of thin films for various devices like sensors, solar cells, light-emitting diodes has received immense interest of
scientific community since many years. In general, thin films are deposited on amorphous substrate (i.e. glass). To overcome the
overweight and rigidity of conventional glass substrates, we have observed an increasing interest in the choice of a specific substrate
that depends on the temperature of deposition and post deposition processing. The use of polymer as a substrate can be introduced in
the preparation of flexible displays and electronic devices [1–3]. Recently, the deposition of metal oxides, like ZnO [4,5] and SnO2 [6],
on a flexible substrate has been reported which has received remarkable industrial applications of such devices. Additionally, several
polymers such as polyethylene terephthalate (PET) [7] and polyethylene naphthalate (PEN) [4] are also used as flexible polymer
substrates.
* Corresponding author. Faculty of Science of Sfax, B.P: 1171 3038, Sfax, University of Sfax, Tunisia.
E-mail address: [email protected] (S. Ben Ameur).
https://doi.org/10.1016/j.spmi.2020.106473
Received 18 November 2019; Received in revised form 25 January 2020; Accepted 27 February 2020
Available online 28 February 2020
0749-6036/© 2020 Elsevier Ltd. All rights reserved.
Superlattices and Microstructures 142 (2020) 106473
S. Ben Ameur et al.
Fig. 1. XRD pattern of Sb2S3 thin films: (a) Sb2S3/PEI and (b) Sb2S3/glass.
Antimony trisulphide (Sb2S3) is an interesting coating material due to its suitable optical properties; direct band-gap Eg of about
1.7–2.5 eV and high absorbance coefficients in the visible region (α~ 104 cm 1) [8]. These properties make Sb2S3 one of the most
promising candidates for the fabrication of extremely thin absorber in solar cells [9–11]. Several research reports describe the growth
of Sb2S3 thin films on various substrates such as glass [8], FTO [12] etc; However, the growth of Sb2S3 thin films on the flexible polymer
substrate has never been reported as per our knowledge. The choice of a specific substrate becomes essential in order to support the
deposition temperature higher than the room temperature. Polyetherimide (PEI) can be adopted as an alternative substrate in com­
parison to the conventional glass because of its high glass transition temperature (Tg ¼ 220 � C), excellent optical transparency and
mechanical properties [13]. Temperature is a key factor for the deposition of a material on the polymeric substrates. In this regard, a
low-temperature technique such as chemical bath deposition is considered to be very promising method for flexible substrates. S. Shaji
et al. [14] have demonstrated the achievement of high crystalline quality of Sb2S3 thin films by chemical bath deposition (CBD) at low
temperature. This reported technique is cheaper as compared to other expensive physical deposition processes such as Vacuum
Thermal Evaporation (VTE). Furthermore, CBD is a soft solution process that can produce high-quality thin films at relatively low
temperature since it is relatively simple, cost-effective and permits easy processing [9,15]. The deposition rate and hence thickness of
the deposited film can be precisely controlled by varying pH, reaction time, temperature and concentration of the solution.
In the present work, we report the Structural, morphological and optical evolution of Sb2S3 thin films deposited by the CBD method
as a function of nature of substrate and thickness. Structural parameters and growth orientations are investigated by X-ray diffraction
(XRD). The optical and dispersion parameters are estimated from the UV–Visible absorption spectroscopy. In particular, this article
emphasizes a correlation between the physical parameters and super-hydrophobic character of thin films. The results obtained with
the CBD deposited Sb2S3/PEI thin films suggest their potential applications in the self-cleaning windows and solar panels.
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Fig. 2. Texture coefficients TC of Sb2S3 thin films: (a) Sb2S3/PEI and (b) Sb2S3/glass.
2. Experiments details
Sb2S3 thin films were prepared on both flexible polymer Polyetherimide (PEI) and glass substrates simultaneously, using a simple
chemical bath deposition technique (CBD). The growth of Sb2S3 thin films is based on the reaction of Sb and S precursors at controlled
temperature T ¼ 60 � C in a weakly acidic bath (pH ¼ 3.8). The chemical bath containing 650 mg of SbCl3 was dissolved in 10 ml of
acetone and 25 ml of 1 M Na2S2O3 and 65 ml of bi-distilled water. H. Maghraoui-Meherzi et al. [15,16] presented a detailed study on
the chemical bath deposition of Sb2S3 thin films and the variation of deposition time with the thickness of thin films which estimated
the thickness of films by the double weight method. In this present investigation, the thicknesses for films were found to be � 300, 600
and 1300 nm. The different time deposition was ranging from 3 to 30 min. For obtaining film thickness around 600 nm, the time
deposition was about 10 min. In the text below, we termed A, B, and C for the samples deposited on PEI substrate having thicknesses of
300 nm, 600 nm, and 1300 nm respectively, and we named A’ (300 nm), B’ (600 nm) and C’ (1300 nm) for the samples deposited on
glass substrate.
Thickness
300 nm
600 nm
1300 nm
Sb2S3/PEI
Sb2S3/glass
A
A0
B
B0
C
C0
Structural, morphological and optical properties of the prepared Sb2S3 thin films were investigated. Hence, the structural pa­
rameters and their orientation were studied by means of X-ray diffractometer (Analytical X Pert PROMPD) having Cu-kα radiation (λ ¼
1.5406 Å). An atomic force microscope (AFM-Brüker Multimode) was used in the contact mode to obtain the morphological infor­
mation. The surface wettability of Sb2S3 was examined through the water Contact Angle (CA) measurements using a contact angle
meter (Micro-Drop analysis DSA 100 M) at ambient temperature. The optical transmittance and reflectance were measured by
UV–Vis–NIR spectrophotometer (Shimadzu UV 3100 S) in the wavelength range from 350 to 1600 nm. The optical constants and
dispersion parameters have been estimated from the transmittance and reflectance spectra of Sb2S3 thin films.
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Fig. 3. Contact angle measurement of PEI, glass substrates and all Sb2S3 thin films.
3. Results and discussions
3.1. Structural properties
X-ray diffraction patterns of Sb2S3 thin films deposited on PEI polymer substrate and on glass substrates with different thicknesses
are shown in Fig. 1(a and b) respectively. All peaks were indexed to the standard diffraction planes based on standard JCPDS powder
diffraction data sets (78–1347) and revealed that the prepared thin films ofSb2S3 are polycrystalline in nature having orthorhombic
structure. No other peaks related to impurities have been observed which indicates the formation of high purity Sb2S3 binary phase.
The XRD patterns of Sb2S3 samples deposited on PEI (Sb2S3/PEI) showed a broad diffuse peak attributed to the amorphous structure of
the PEI polymer. The samples show different preferential orientations. In general, preferential orientations are in turn affected by the
growth conditions such as film thickness, temperature, topographical and nature of substrate [10,16,17]. Hence, the preferential
growth orientation of the polycrystalline Sb2S3 thin films can be estimated from the texture coefficient TC (hkl) calculation using the
following relation [10]:
TCðhklÞ ¼
N
IðhklÞ =I0 ðhklÞ
P
IðhklÞ =I0ðhklÞ
(1)
1
Where, I(hkl) is the measured intensity for (hkl) diffracting plane, I0(hkl) is the corresponding intensity for a randomly oriented sample
taken from the JCPDS card and N is the number of observed diffraction peaks. The variation of the texture coefficient of all Sb2S3 thin
films is shown in Fig. 2. Our first motive is to understand the effect of substrate on the nature of thin films which is discussed as follows:
It is clear that the substrate nature significantly affects the general texture and the preferred orientation of the films. We have noted
a change in the orientation, appearance and disappearance of the preferential growth on a plane. This change can be correlated to the
morphology and the adhesion character of the substrate. To disclose this correlation, the surface properties of PEI and glass substrates
were investigated using the CA measurement which is shown in Fig. 3. It’s clear that the PEI polymer substrate surface (θ ¼ 76� ) is more
hydrophobic as compared to the glass (θ ¼ 50� ). The variation of the hydrophobicity character is due to the difference in the adhesion
forces (Johannes D. van der Waals forces) between the water and the solid surface. Indeed, it is noted that the PEI substrate has the
lower adhesive character with higher adhesion force (118.8 � 10 3 N/m) as compared to glass one (96.3 � 10 3 N/m). Furthermore,
during the film formation, the interaction between the atoms and the substrate is different for the various substrates. These changes
reflect in the thermo-dynamical character of film formation [17,18]. The extrinsic constraint is another parameter that causes the
different orientations of the films during their growth due to the interaction between the substrate and the film. The principal origin of
these constraints is the difference between the coefficients of thermal dilatation of the substrates. The coefficients of thermal dilatation
for the glass and PEI are found to be 9 � 10 6(� C 1) and 56 � 10 6 (� C 1), respectively.
In our second motive, we have investigated the role of film thickness on the preferential growth of the films. On the same substrate,
the preferential orientation of films changes with the thickness of the films. The change in crystallite preferred orientation of the films
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Table 1
Micro-structural parameters of all Sb2S3 thin films on PEI substrate.
sample
D (nm)
δ (10
A
B
C
A0
B0
C0
74
63
83
162
138
102
13.5
15.8
12
6.1
7.2
9.8
3
) nm
2
ζ (10 4)
RMS (nm)
8.8
11.3
3.5
2.8
2. 9
1.5
136
116
90
57
33
22
Fig. 4. 2D and 3D AFM images of all Sb2S3 thin films.
can be explained by the atomic rearrangement of the films.
Additionally, as the microstructure is extremely important and determines the main properties of thin films including their elec­
trical, mechanical, and optical characteristics, we have proceeded to determine the microstructural parameters of the prepared Sb2S3
films. Likewise, from the XRD analysis, we determined the microstrain (ζ) as well as the microstructural parameters such as the average
crystallite size (D) and the dislocation density (δ). So, the full width at half-maximum (β) can be used to estimate the average crystallite
size of all Sb2S3 thin films using Scherrer’s formula [19]:
D¼
0:9λ
β cos θ
(2)
Where λ is the wavelength of X-ray source.
The structural defects such as the dislocation density (δ), which is defined as the length of dislocation lines per unit volume of the
crystal, and the microstrain (ζ) induced in the film due to crystal defects such as lattice dislocations, are calculated from the following
expressions [19]:
δ¼
1
D2
(3)
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Table 2
Optical band gap Eg and Urbach energies Eu values.
ε¼
sample
Eg (eV)
Eu (meV)
A
B
C
A0
B0
C0
1.95
1.74
2.00
1.63
1.74
2.15
525
550
462
507
408
331
β
4 tanðθÞ
(4)
The calculated micro-structural parameters have been illustrated in Table 1.
It is clear from the results listed in Table 1 that the Sb2S3/PEI thin films have an average crystallite size varied from 63 to 83 nm
which is smaller than the Sb2S3/glass films having size from 102 to 162 nm. Besides, it is obvious that the Sb2S3/glass thin films have
lower microstrain and the dislocation density values due to their large crystallite size. The glass substrate encourages the formation of
more relaxed Sb2S3 thin films. For the Sb2S3/PEI thin films, we observed that the crystallite size increases with the increasing film
thickness, simultaneously with a decrease in the micro-strain values, which indicates a decrease in the concentration of the lattice
imperfections [20,21]. Accordingly, larger D, smaller δ and ζ values indicate a high crystalline quality of the sample C. For the
Sb2S3/glass, we noted a decrease in the crystallite size and in micro-strain values when the thickness increases.
3.2. Morphological properties
The morphological characterization of the Sb2S3 films was carried out using atomic force microscopy (AFM). Fig. 4 shows the 2D
and 3D AFM images (10 μm � 10 μm) of all Sb2S3/PEI and Sb2S3/glass thin films. Sample (A) exhibits a heterogeneous and extremely
rough surface. For all Sb2S3 thin films, we observed the random distribution of almost-spherical grains. However, the Sb2S3/glass thin
films are more multi-grained and showed uniform growth of thin films over the substrate surface.
All thin films show rough surfaces with the different root mean square (RMS) roughness values. For Sb2S3/PEI thin films, the
average RMS roughness values have been found to vary between 90 nm and 136 nm. Whereas, we noted a lower roughness with RMS
values less than 60 nm for the Sb2S3/glass (Table 2). PEI substrate causes higher roughness than the glass substrate. A. Karimi et al.
[22] have shown that ZnS thin films deposited on PS are rougher than that of deposited on the glass substrate. It is a fact that the films
are grown uniformly on the rough polymer substrate; consequently, producing different morphologies [23]. On the other hand, we
have assumed that the structural variations such as the texture and micro-structural parameters reveal a significant variation in the
morphology of thin films. This means that the surface morphology of the substrate can be strongly influenced by the thickness. For both
Sb2S3/glass and Sb2S3/PEI, the RMS values decrease with the increasing films thickness.
The specific morphological properties of Sb2S3 films prepared by CBD lead to a hydrophobic character. This feature is required for
many applications like self-cleaning surface.
3.3. Surface hydrophobicity
Controlling the surface hydrophobicity is an essential challenge for a wide range of possible applications such as self-cleaning
fabrics, friction reduction in micro-fluidic devices, self-cleaning glass for windows, windshields and solar panels [23,24]. Wetta­
bility is the most important property of the solid surfaces. It is commonly quantified by measuring CA which involves the interaction
between a liquid and a solid in contact.
Using Young’s relation [25], we can determine the CA as follows:
cos θ ¼
γ sl Þ
ðγ sv
(5)
γ lv
Where γ sv , γ sl , and γ lv refer to the interfacial tensions for the solid–vapor, solid–liquid and liquid–vapor, respectively. Equilibrium
contact angle θ is a result of the thermodynamic equilibrium of the free energy at the solid-liquid-vapor interface. The shape of a water
droplet on the film is shown in Fig. 3.
In this study, CA measurements reveal that all Sb2S3/PEI samples have a hydrophobic character (CA> 90� ) with super-hydrophobic
character for sample B (CA¼162� > 150� ). Nonetheless, Sb2S3/glass thin films exhibit hydrophilic behavior (CA<90� ). This is probably
due to the considerable change in the surface morphology. V.R. Shinde et al. [26] have explained the increase of water contact angle in
case of non-spherical nature of the grains and topographical changes in the structure. These results are in accord with the AFM
demonstration. Hence, as mentioned above, wettability is influenced by the physicals properties namely-surface morphology and
surface chemistry [27]. Terriza et al. [28] have established a direct correlation between the roughness and water contact angle for the
fluorocarbon materials whereas the superhydrophobic behavior was only found for the films having very roughness. It is proposed that
the different surface wettability of Sb2S3 thin films should be ascribed to different surface roughness essentially due to the grown
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Fig. 5. Transmittance and reflectance spectra: (a)Sb2S3/PEI thin films and (b) Sb2S3/glass thin films.
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Fig. 6. Optical band gap energies of Sb2S3 thin films.
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Fig. 7. Extinction coefficient k(λ) and Refraction index n(λ): (a)Sb2S3/PEI and (b) Sb2S3/glass thin films.
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textures of thin films. So, the higher RMS values of Sb2S3/PEI thin films allow to obtain a superhydrophobic surface. The results suggest
that the control of surface roughness is an effective approach to obtain a superhydrophobic film. Furthermore, the superhydrophobic
character of Sb2S3 surface thin films makes this material a potential candidate for many a new set of applications including
self-cleaning, anti-icing, antibacterial, oil-water separation, corrosion resistance, etc [29–31].
3.4. Optical properties
Further improvements in solar cells using Sb2S3 film as an absorber layer require a deep understanding of the opto-electronic
behavior of antimony trisulfide. The transmittance and the reflectance spectra of all Sb2S3 thin films in the region of 350–1600 nm
wavelength are shown in Fig. 5. The transmittance spectra show that the Sb2S3/glass thin films are more transparent with that of the
deposited on PEI in the visible and NIR regions. The prepared thin films yield the transmission between 40% and 60%. These results are
in agreement with the previously reported articles [10,14]. On the other hand, for all films, the reflectance is very low in the
wavelength range below to 600 nm, whereas it has highest values between 600 and 800 nm. In the NIR region, reflectance decreases
with the wavelength. The adsorption coefficient of Sb2S3 thin films is determined from transmittance and reflectance data using the
following expression [20]:
3
2
�12
�
2
4
2
2
7
1 6ð1 RÞ þ ð1 þ RÞ þ 4R T
7
α ¼ Ln6
(6)
5
e 4
2T
=
Where, e is the film thickness, R is the reflectance and T is the transmittance of the film.
All Sb2S3thin films show high optical absorption coefficient of order more than 104 cm 1which is a suitable factor for the solar cell
applications. The optical band gap energies(Eg)of the films are determined using the Tauc relationship [21]:
ðαhνÞ2 ¼ Aðhν
(7)
EgÞ
Where A is a constant and (hν) is the incident energy.
The intersection of the extrapolation of the linear part of the curves on the x-axis leads to the optical band gap values which are
shown in Fig. 6. The estimated band gap values of all the samples are listed in Table 2. Noticeably, the band gap energy values for all
Sb2S3 thin films are around 1.63 eV and 2.15 eV. These Eg values are similar to the earlier reported Sb2S3 thin films deposited with
chemical methods [19,20,32,33]. The variation in band gap values as a function of thickness can be related to the variation of
structural defects in the compound which will be confirmed by the Urbach energy values. Thus, Urbach energy (Eu) characterizes the
local defects introducing the localized electronic states in the band gap which is determined from the following empirical formula [34]:
LnðαÞ ¼ Lnðα0 Þ þ
hν
Eu
(8)
Where,α0 is a constant.
The Eu values are listed in Table 2. We can note that Sb2S3/glass substrates have lower disorder as well as the lower Eu values. This
result matches well with the microstructural lattice disorder as mentioned in XRD section which has confirmed the encouragement of
the growth of thin films on the glass substrate.
It is clear that this variation is nonlinear to the thickness dependence and we can relate the variation of Eg and Eu to the crystalline
defects. The correlation of those parameters implies that the structural defects reduce the band gap of the films and increases the Eu by
the formation of localized states in the band gap [35].
Furthermore, the refractive index n (λ) and the extinction coefficient k (λ)can be determined from the following equation using the
absorption data [36]:
�
� sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
1þR
4R
þ
(9)
n¼
k2
1 R
ð1 RÞ2
k¼
αλ
4π
(10)
Fig. 7 shows the dispersion of the refractive index (n) and the extinction coefficient (k) of all Sb2S3 thin films in the wavelength
range of 400–1600 nm. The n values are in the range of 2.0–3.6 for all the thin films in the visible and NIR regions. In addition, Sb2S3
thin films exhibit low values of the extinction coefficient k, which indicates the low energy losses in these films. For Sb2S3/glass, the
thinner films have the lower optical loss. While, for films prepared on PEI the thickest one exhibits a lower energy loss. In general, the
extinction coefficient represents the energy losses and is related to the crystalline quality and surface morphology of the sample.
Furthermore, it can be observed that the Sb2S3 film that has the lower k values exhibits the higher transmittance and lower scattering of
photons as mentioned previously.
The dielectric functions(ε*) of all Sb2S3 thin films, which depend on the optical functions, refractive index (n) and extinction
coefficient (k), can be written as follows [36]:
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Fig. 8. ε1versus λ2 and ε2 versus λ3.
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Table 3
�
Values of ε∞ , ωp, τ and N * for Sb2S3 thin film.
me
sample
ε∞
ωp (1014 rad s 1)
τ(s)
A
B
C
A0
B0
C0
16.00
17.28
17.06
15.05
16.3
15.9
10.45
10.14
10.07
9.32
8.6
9.04
7.69 10 15
4.7 10 15
5.9 10 12
6.57. 10 15
3.7 10 15
5.69 10 15
ε1 ðλÞ ¼ n2 ðλÞ
N� * (1047 g
me
1
cm 3)
4.81
0.55
0.53
5.32
0.67
0.78
(11)
k2 ðλÞ
(12)
ε2 ðλÞ ¼ 2nðλÞkðλÞ
Where, ε1 and ε2 are the real and imaginary parts of the complex dielectric function (ε*).
In Fig. 8, it is found that in infrared region, the dispersion of ε1is linear as a function of the square of the wavelength (λ2), while the
absorption ε2 is linear with λ3.
In the near infrared region using the classical theory, the dielectric constants are expressed by the following equations [37]:
ε1 � ε∞
ε2 �
ε∞ ω2p
4π2 c2
(13)
λ2
ε∞ ω2P 3
λ
8π3 c3 τ
(14)
Where ε∞ is the dielectric constant at high frequencies, ωp is the plasma pulsation and τ is the relaxation time. ε2 has a low value which
proves that the energy loss of light through thin films is weak. The dielectric constant (ε∞) shows a slight increase with thickness as it
can be seen in Table 3. From the slope of these curves (Fig. 8), we have deduced the values of ωp (Table 3) which decreases slightly with
the thickness. In the same way, from the slope of the linear dependence of the ε2 (λ3) and the knowledge of ωp, we have determined the
relaxation time (τ) whose values are given in Table 3. It is noticed that the relaxation time increased drastically from 10 15 to 10 12 s
for the thickest film C. All these observations are linked to the structural changes as previously mentioned. In fact, C is the most relaxed
sample, thus it is in relatively stable state compared to the other films. Afterward, the values of the free carrier concentration to
effective mass ratio N=m*e are calculated from the following relation [37]:
ω2p ¼
4πNe2
ε∞ m*e
(15)
The free carrier concentration to effective mass ratio N=m*e decreases with the thickness for wavelength ranging from 600 nm to
1300 nm. This is related to the microstructure evolution of Sb2S3 films with thickness as well as the nature of substrate. In Fact, as it
was already demonstrated by DRX analysis, accordingly, larger crystallite size (D), and smaller dislocation density δ values indicate
high crystalline quality of the film, which indicates a decrease in the concentration of the lattice imperfections [19,20].
4. Conclusion
In summary, Sb2S3thin films on PEI flexible polymer and glass substrates with various thicknesses (i.e. 300, 600 and 1300 nm) have
been successfully synthesized by a simple chemical bath deposition technique. The prepared thin films have also been characterized by
X-ray diffraction (XRD), atomic force microscopy (AFM), contact angle (CA) measurements and UV–visible optical spectroscopy. Our
investigation reveals that the orientational growth and structural parameters of thin films significantly depend on the nature of the
substrate. X-ray diffractographs have confirmed the formation of orthorhombic polycrystalline films. Sb2S3/PEI thin films are found to
be rougher as compared to those of Sb2S3/glass. The higher roughness of Sb2S3/PEI thin films leads to their super-hydrophobic
character. Using the optical spectroscopy, we have confirmed that all thin films show high absorption coefficient of order higher
than 104 cm 1. Additionally, energy band gap of these films has also been calculated and found to be in between 1.6 and 2.1 eV. Using
the complex dielectric function, the refractive index and extinction coefficient of the Sb2S3 thin films have been evaluated. In this
article, a correlation between the optical and structural properties of Sb2S3 thin films has been discussed in detail. These thin films have
shown their potential applications for the next-generation solar cells, self-cleaning windows and flexible optical devices.
Authors statement
All listed authors are aware of this communication. These results are only submitted to Superlattices and Microstructures for the
consideration of publication and not under consideration elsewhere.
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Declaration of competing interest
All listed authors are aware of this communication and we also declare no conflict of interest for this article.
Acknowledgements
The authors would like to express their gratitude for the financial support from the Ministry of High Education and Scientific
Research in Tunisia
Appendix A. Supplementary data
Supplementary data to this article can be found online at https://doi.org/10.1016/j.spmi.2020.106473.
References
[1] D.Y. Kim, S. Lee, Z.-H. Lin, K.H. Choi, S.G. Doo, H. Chang, J.-Y. Leeme, Z.L. Wang, S.-O. Kim, High temperature processed ZnO nanorods using flexible and
transparent substrates for dye-sensitized solar cells and piezoelectric nanogenerators, Nanomater. Energy 9 (2014) 101–111, https://doi.org/10.1016/j.
nanoen.2014.07.004.
[2] Mouad Ouafi, Boujema^
a Jaber, Larbi La^
anab, Low temperature CBD growth of CdS on flexible substrates: structural and optical characterization, Superlattice.
Microst. 129 (2019) 212–219, https://doi.org/10.1016/j.spmi.2019.03.024.
[3] Lukas Kinner, Martin Bauch, Rachmat Adhi Wibowo, Giovanni Ligorio, J. Emil, W. List-Kratochvil, Theodoros Dimopoulos, Polymer interlayers onflexible PET
substrates enabling ultra-highperformance, ITO-free dielectric/metal/dielectric transparent electrode, Mater Des. 168 (2019), 106773, https://doi.org/
10.1016/j.matdes.2019.107663.
[4] S. Hamrit, K. Djessas, N. Brihi, B. Viallet, K. Medjnoun, S.E. Grillo, The effect of thickness on the physico-chemical properties of nanostructured ZnO: Al TCO thin
films deposited on flexible PEN substrates by RF-magnetron sputtering from a nanopowder target, Ceram. Int. 42 (2016) 16212–16219, https://doi.org/
10.1016/j.ceramint.2016.07.143.
[5] S. Ben Ameur, A. Barhoumi, R. Mimouni, M. Amlouk, H. Guermazi, Low-temperature growth and physical investigations of undoped and (In, Co) doped ZnO
thin films sprayed on PEI flexible substrate, SuperlatticesMicrostruct 84 (2015) 99–112, https://doi.org/10.1016/j.spmi.2015.04.028.
[6] S. Ben Ameur, A. Barhoumi, H. BelHadjltaief, R. Mimouni, B. Duponchel, G. Leroy, M. Amlouk, H. Guermazi, Physical investigations on undoped and Fluorine
doped SnO2 nanofilms on flexible substrate along with wettability and photocatalytic activity tests, Mater. Sci. Semicond. Process. 61 (2017) 17–26, https://doi.
org/10.1016/j.mssp.2016.12.019.
[7] S. Lee, C. Yang, J. Park, The effect of the surface physical properties of polymer substrates on the adhesion and cracking of transparent conductive oxide (TCO)
coatings, Surf. Coating. Technol. 207 (2012) 24–33, https://doi.org/10.1016/j.surfcoat.2012.03.070.
[8] Wei Zhang, Miao Tan, Ping Zhang, Lina Zhang, Weinan Dong, Qiushi Wang, Jinwen Ma, Enlai Dong, Shichong Xu, Guiqiang Wang, One post synthesis of Sb2S3
nanocrystalline films through a PVP-assisted hydrothermal process, Appl. Surf. Sci. 455 (2018) 1063–1069, https://doi.org/10.1016/j.apsusc.2018.06.084.
[9] S.M. Pawar, B.S. Pawar, J.H. Kim, O.-S. Joo, C.D. Lokhande, Recent status of chemical bath deposited metal chalcogenide and metal oxide thin films, Curr. Appl.
Phys. 11 (2011) 117–161, https://doi.org/10.1016/j.cap.2010.07.007.
[10] F. Aousgi, W. Dimassi, B. Bessais, M. Kanzari, Effect of substrate temperature on the structural, morphological, and optical properties of Sb2S3 thin films, Appl.
Surf. Sci. 350 (2015) 19–24, https://doi.org/10.1016/j.apsusc.2015.01.126.
[11] Chunhui Gaoa, Jialiang Huangb, Huangxu Lia, Kaiwen Sunb, Yanqing Laia, Jiaa Ming, Liangxing Jianga, Fangyang Liu, Fabrication of Sb2S3 thin films by
sputtering and post-annealing for solar cell, Ceram. Int. 45 (2019) 3044–3051, https://doi.org/10.1016/j.ceramint.2018.10.155.
[12] bing Wei, Beibei Wu, Kai Shan, Feng Huilin Nan, Resistive switching behavior of Sb2S3 thin film prepared by chemical bath deposition, Mater. Sci. Semicond.
Process. 44 (2015) 18–22, https://doi.org/10.1016/j.mssp.2015.12.031.
[13] N. Mzabi, H. Smaoui, H. Guermazi, Y. Mlik, S. Agnel, Al Toureille, Heating effects on structural and electrical properties of polyetherimide, Am. J. Eng. Appl.
Sci. 2 (1) (2009), https://doi.org/10.1002/pi.21352.
[14] S. Shaji, L.V. Garcia, S.L. Loredo, B. Krishnan, J.A. Aguilar Martinez, T.K. Das Roy, D.A. Avellaneda, Antimony sulfide thin films prepared by laser assisted
chemical bath deposition, Appl. Surf. Sci. 393 (2017) 369–376, https://doi.org/10.1016/j.apsusc.2016.10.051.
[15] H. Maghraoui-Meherzi, T. Ben Nasr, N. Kamoun, M. Dachraoui, Physical properties of chemically deposited Sb2S3 thin films, C. R. Chimie 14 (2011) 471–475,
https://doi.org/10.1016/j.crci.2010.10.007.
[16] H. Maghraoui-Meherzi, T. Ben Nasr, N. Kamoun, M. Dachraoui, Structural, morphology and optical properties of chemically deposited Sb2S3 thin films, Physica
B 405 (2010) 3101–3105, https://doi.org/10.1016/j.physb.2010.04.020.
[17] Ostadi Ali, Seyyed Hojjatollah Hosseini, Mohammadreza Ebrahimi Fordoei, The effect of temperature and roughness of the substrate surface on the
microstructure and adhesion strength of EB-PVD ZrO2-%8wtY2O3 coating, Ceram. Int. 46 (2020) 2287–2293, https://doi.org/10.1016/j.ceramint.2019.09.217.
[18] V. Consonni, G. Rey, H. Roussel, B. Doisneau, E. Blanquet, D. Bellet, Preferential orientation of fluorine-doped SnO2 thin films: the effects of growth
temperature, Acta Mater. 61 (2013) 22–31, https://doi.org/10.1016/j.actamat.2012.09.006.
[19] Nripasree Narayanan, N.K. Deepak, Enhancement of visible luminescence and photocatalytic activity of ZnO thin films via Cu doping, Optik 158 (2018)
1313–1326, https://doi.org/10.1016/j.ijleo.2018.01.024.
[20] M. Haj Lakhdar, B. Ouni, M. Amlouk, Thickness effect on the structural and optical constants of stibnite thin films prepared by sulfidation annealing of antimony
films, Optik 125 (2014) 2295–2301, https://doi.org/10.1016/j.ijleo.2013.10.114.
[21] R.S. Mane, C.D. Lokhande, Thickness-dependent properties of chemically deposited Sb2S3 thin films, Mater. Chem. Phys. 82 (2003) 347–354, https://doi.org/
10.1016/S0254-0584(03)00271-2.
[22] A. Karimi, B. Sohrabi, M.R. Vaezi, Highly transparent, flexible and hydrophilic ZnS thin films prepared by a facile and environmentally friendly chemical bath
deposition method, Thin Solid Films 651 (2018) 97–110, https://doi.org/10.1016/j.tsf.2018.02.021.
[23] Seung-Ho Lee, Chan-Woo Yang, Jin-Woo Park, The effect of the surface physical properties of polymer substrates on the adhesion and cracking of transparent
conductive oxide (TCO) coatings, Surf. Coating. Technol. 207 (2012) 24–33, https://doi.org/10.1016/j.tsf.2011.08.081.
[24] Jiao Xie, Hu Jia, Liang Fang, Xiaoling Liao, Ruolin Du, Fang Wu, Liang Wu, Facile fabrication and biological properties of super-hydrophobic coating on
magnesium alloy used as potential implant materials, Surf. Coating. Technol. 384 (2020) 125223, https://doi.org/10.1016/j.surfcoat.2019.125223.
[25] D.J. Marchand, Z.R. Dilworth, R.J. Stauffer, E. Hsiao, J.-H. Kim, J.-G. Kang, S.H. Kim, Atmospheric rf plasma deposition of superhydrophobic coatings using
tetramethylsilane precursor, Surf. Coating. Technol. 234 (2013) 14–20, https://doi.org/10.1016/j.surfcoat.2013.03.029.
[26] V.R. Shinde, C.D. Lokhande, R.S. Mane, Sung-Hwan Han, Hydrophobic and textured ZnO films deposited by chemical bath deposition: annealing effect, Appl.
Surf. Sci. 245 (2005) 407–413, https://doi.org/10.1016/j.apsusc.2004.10.036.
13
Superlattices and Microstructures 142 (2020) 106473
S. Ben Ameur et al.
[27] H. Ji, G. Chen, J. Yang, J. Hu, H. Song, Y. Zhao, A simple approach to fabricate stable superhydrophobic glass surfaces, Appl. Surf. Sci. 266 (2013) 105–109,
https://doi.org/10.1016/j.surfcoat.2015.07.002.
�
[28] A. Terriza, R. Alvarez,
A. Borr�
as, J. Cotrino, F. Yubero, A.R. Gonz�
alez-Elipe, Roughness assessment and wetting behavior of fluorocarbon surfaces, J. Colloid
Interface Sci. 376 (2012) 274–282, https://doi.org/10.1016/j.jcis.2012.03.010.
[29] X. Zhong, H. Zhao, H. Yang, Y. Liu, G. Yan, R. Chen, Tunable surface wettability and water adhesion of Sb2S3 micro-/nanorod films, Appl. Surf. Sci. 289 (2014)
425–429, https://doi.org/10.1016/j.apsusc.2013.10.179.
[30] Mohammad Liravi, Hossein Pakzad, Moosavi Ali, Ali Nouri-Borujerdi, A comprehensive review on recent advances in superhydrophobic surfaces and their
applications for drag reduction, Pr.Org.Coat. 140 (2020), 105537, https://doi.org/10.1016/j.porgcoat.2019.105537.
[31] Xiaowei Xun, Yizao Wan, Quanchao Zhang, Deqiang Gan, Jian Hu, Honglin Luo, Low adhesion superhydrophobic AZ31B magnesium alloy surface with
corrosion resistant and anti-bio adhesion properties, Appl. Surf. Sci. (2019), https://doi.org/10.1016/j.apsusc.2019.144566.
[32] A.N. Kulkarni, M.B.R. Prasad, R.V. Ingle, H.M. Pathan, G.E. Eldesoky, M. Naushad, R.S. Patil, Structural and optical properties of nanocrystalline Sb2S3 films
deposited by chemical solution deposition, Opt. Mater. 46 (2015) 536–541, https://doi.org/10.1016/j.optmat.2015.04.066.
[33] F. Aousgi, M. Kanzari, Study of the optical properties of Sn-doped Sb2S3 thin films, Energy Procedia 10 (2011) 313–322, https://doi.org/10.1016/j.
egypro.2011.10.197.
[34] R. Boughalmi, A. Boukhachema, M. Kahlaoui, H. Maghraoui, M. Amlouk, Physical investigations on Sb2S3 sprayed thin film for optoelectronic applications,
Mater. Sci. Semicond. Process. 26 (2014) 593–602, https://doi.org/10.1016/j.mssp.2014.05.059.
[35] B. Ouni, M. Zouini, M. Haj Lakhdar, T. Larbi, W. Dimassi, M. Amlouk, Preparation and characterization of the rod-shaped stibnite, Mater. Res. Bull. 67 (2015)
191–195, https://doi.org/10.1016/j.materresbull.2015.03.003.
[36] M.A. Omar, Elementary Solid State Physics, Addison-Wesley Publishing Company, 1993.
[37] A. Souissi, M. Amlouk, S. Guermazi, ZnO: Mo: in nanofilms on SiO2 substrate under investigation framework of the second optical transition, Opt. Mater. 64
(2017) 502–511, https://doi.org/10.1016/j.optmat.2017.01.009.
14